09/08/2007
Coolant: the Pros and Cons in modern machining
The necessity of cooling lubricants in the cutting tool sector |
 |
Wet or dry? This is a frequently asked question with regard to machining processes. Dry machining is desirable but cannot be applied to all work piece materials, then wet machining is applied and emulsion and/or oil is used as a cooling lubricant. The problem: in case of high temperatures cooling lubricants lead to chemical reactions and the disposal of contaminated chips and liquids requires additional costs and effort. For years CERATIZIT has therefore offered solutions for the reduction of coolant quantity and for dry machining.
Take-off with the aerospace industry: aluminium machining with minimum quantity lubrication
It was twenty years ago that the coolant quantity the field of aluminium machining began to decrease. The aerospace industry took the initiative and started machining with minimum quantity lubrication. In this method the mixture of air and liquid, also called aerosol, was sprayed in the direction of the cutting edge. The result was virtually dry chips, extremely low coolant consumption and acceptable tool life combined with high cutting speed.
CERATIZIT is one of the main suppliers for HSC tools in the aerospace sector. When developing these tools mainly aerospace components made of high-tensile aluminium alloys were applied with minimum quantity lubrication. The result: the tools are suitable for wet machining, minimum quantity lubrication and dry machining. The CERATIZIT tooling systems HSC/HPC19 and HSC11 are currently considered the benchmarks in high-speed milling and high-performance milling.
Wear resistant, heat resistant, tough: HyperCoat C for the machining of steel and cast iron
Dry turning of steel at high speed represented another big challenge. The main problems in this context were the high temperatures during the machining processes (up to 1,200°C on the cutting edge) and the adhesion of the work piece material to the cutting material in the cutting edge area. In order to prevent plastic deformation of the carbide at high temperatures the CERATIZIT research department developed special carbide compositions with a low share of cobalt binder and an increased share of cubic carbides such as TaC, NbC, TiC and ZrC. In the peripheral zone of the carbide substrate they were combined with special gradients (e.g. CTC1110, CTC1115 and CTC1125). Particularly the new grade CTC1130 of the innovative HyperCoat C series with its special surface morphology allows a substantially reduced lubricant quantity in the P30 area, as the tendency to stick was considerably reduced.
The contrary ones: super alloys and titanium
Until today materials like high alloyed steel, super alloys and in particular titanium have ‘defended themselves’ successfully against dry machining. It is not even possible to reduce the coolant or lubricant quantity. Therefore swarf adhesion, chip evacuation and chemical reactions between cutting material and work piece have to be analysed. For the production of titanium components the tool design has been adapted. Large chip flutes and coolant holes optimised for chip evacuation, specifically shaped chip grooves of the inserts and the new grade CTP5240 which is part of the HyperCoat P line ensured notable increases in performance, i.e. higher chip removal rates when wet machining.
Definitely both is possible
Dry machining? The answer is yes and no. There are very successful applications in dry machining. Nevertheless there are application fields where cooling and lubrication will remain indispensable in the near future. Manufacturers and tooling suppliers will therefore have to develop additional solutions together.
|
Specials
